Biochronostratigraphy of the Reingraben Turnover (Hallstatt Facies Belt): Local black shale events controlled by regional tectonics, climatic change and plate tectonics

摘要

For the first time, two outcrops near Bad Dürrnberg (2 km SSW Hallein, Austria) allowed for a continuous multistratigraphical investigation of the Reingraben Turnover in the Hallstatt facies belt. After a phase of reefal sedimentation during the Julian 1 (Early Carnian), a sudden increase in terrigenous input (Reingraben Turnover) caused the breakdown of the carbonate factory at the beginning of the Julian 2 (late Early Carnian). In starved basins produced by syndepositional tectonism, black shales locally accumulated. Stable isotopes of oxygen and carbon do not suggest a change in seawater chemistry during the turnover. Shallow-water carbonate production resumed slowly during the Tuvalian (Late Carnian), and complete recovery was finished near the Carnian-Norian transition. Because similar events are recorded globally, climatic changes (monsoonal circulation) controlled by plate tectonics are favoured as triggers of the event.